Electronic circuits, and particularly computer and instrumentation circuits, have in recent years become increasingly powerful and fast. For example, a frequency at which a processor runs (Fmax) has increased in recent years from 8 megahertz (Mhz) up to about 3.6 gigahertz (GHz) for current Pentium 4 processors. Often, processors with a higher Fmax have a higher price tag.
As Fmax continues to increase, noise in the power and ground lines increasingly becomes an issue. This noise can arise due to inductive and capacitive parasitics in a power delivery path, for example. To reduce such noise, capacitors known as bypass capacitors are often used to provide a stable signal or stable supply of power to the circuitry. Often capacitors are used to suppress unwanted radiation, to dampen voltage overshoot when an electronic device (e.g., a processor) is powered down, and to dampen voltage droop when the device powers up.
Bypass capacitors are generally placed as close as practical to a die load in order to increase the capacitors' effectiveness by reducing the parasitic inductance. Often, the bypass capacitors are surface-mounted to a land side of a package substrate opposite a die side of the package substrate.